Aneurysms of the thoracic aorta occur relatively infrequently with an occurrence of 10.4 cases per 100,000 person years. For those patients having an untreated aneurysm, aneurysm rupture is the leading cause of death, aneurysm rupture having a mortality rate of 74-94%. The current standard of care for management of ascending and arch thoracic aneurysms greater than 5.5 cm diameter, and descending thoracic aneurysms greater than 6.5 cm diameter is surgery with prosthetic graft replacement. Because of the concomitant comorbidities associated in this group of patients, including coronary artery disease (30%), heart failure (14%), hypertension (72%) cerebrovascular disease (11%), and chronic obstructive airway disease (31%), many of these patients are excluded from being surgical candidates for aneurysm repair because of the prohibitive operative risk. Despite advances in peri-operative care and surgical techniques including the use of left heart bypass, hypothermic circulatory arrest and spinal cord drainage/cooling, the mortality and paraplegia rate may be as high as 35% and 21% respectively.
Advances in the field of endovascular therapy have led to the development of translumenal stent-grafts to treat thoracic aneurysmal disease. Some have demonstrated the feasibility of deploying stent-grafts to treat isolated descending thoracic aneurysms. However, aneurysms isolated to the descending thoracic comprise only 35% of the total, with aneurysms of the ascending aorta (40%), the arch aorta (15%), or mixed (10%) comprising the balance.
The devices currently being inserted are either individually custom made by the interventionalist or, are being investigated in company-sponsored Food and Drug Administration (FDA) trials, such as the Thoracic Excluder™ (W. L. Gore & Assoc.®) or the Talent™ (Medtronic®). The use of these devices is limited to the presence of satisfactory “landing zones” proximal and distal to the aneurysm sac allowing for a sufficient seal to exclude the aneurysm from the circulation. In patients with descending thoracic aneurysms with arch involvement, isolated arch aneurysms, or distal ascending thoracic aneurysms, little possibility currently exists for treatment using an endovascular approach because of the lack of a suitable side-branched stent-graft that can at the same time “straddle” and exclude the aneurysm while maintaining normal blood flow to the brachiocephalic vessels. To date, there are only limited occurrences of successful endovascular placement of triple-branched stent-graft completely across the aortic arch.